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Logic & Scientific Philosophy

Bedtime Syllogism

All beds are for people to sleep on.
A riverbed is a bed.
Therefore a riverbed is for people to sleep on.

The conclusion of this syllogism is valid, as it follows the presented premises. However, this argument is not true, due to the untrue premises. As a result, this argument is not sound.

A: Middle Term = Beds

B: Predicate Term = For people to sleep on

C: Subject Term = A riverbed

This syllogism follows the proper form of a categorical syllogism: All (A) are (B). (C) is an (A). Therefore (C) is a (B).

Though at first glance the first premise may seem true, but due to its lack of clarity and specificity, it is not so. Without defining the word “bed”, the word can refer to any kind of bed, such as “roadbed,” “hotbed”, or “riverbed,” like in the premises. These examples are all some sort of base or foundation in which other materials or substances are placed upon, therefore all fall under the definition of beds. This disapproves that “All beds are for people to sleep on.” Therefore, the first premises is false. In order for this premise to be true, additional information is necessary. For example, if “that are designed for humans” was added on, it would now read: “All beds that are designed for humans are for people to sleep on.” “Roadbed,” “hotbed”, or “riverbed,” would no longer fall under this category of beds.

Though the conclusion is not true, one could still attempt to sleep upon a riverbed. Just because it isn’t for people to sleep on, doesn’t mean it can’t be.

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Discussion

2 thoughts on “Bedtime Syllogism

  1. “The conclusion of this syllogism is valid, as it follows the presented premises.” => should be: “The *argument* is valid, as the conclusion follows from the premises.”

    “However, this argument is not true, due to the untrue premises.” => Should be, simply, “The premises are not true.” Therefore, as you say, the argument is not sound.

    Also, one more thing. You say “Though at first glance the first premise may seem true, but due to its lack of clarity and specificity, it is not so.” It’s not the ‘lack of clarity and specificity’ that makes the premise false. Many sentences lack clarity and specificity, and are still true. For example: “beds are beds.” The sentence is unclear, but it is undeniably true.

    What makes the sentence false is, as you say, the fact that there are many types of ‘bed’ that are not for people to sleep on. Notice how you showed that the premise was false. The premise was ‘All A are B’. You found examples of ‘A’ that are not ‘B’.

    All in all, though, this is a really good analysis of the syllogism, and essentially correct.

    Posted by Stephen Downes | October 4, 2012, 10:41 am
    • Thank you for the corrections, Mr. Downes. I now realize, even more so than before, the importance of correct terminology when used in logic. An argument can be valid and/or sound, but not “true”, simply because “true” cannot be used to describe the argument.
      Thanks again, your wise words will be taken very much to heart.

      Posted by irishung | October 5, 2012, 6:00 am

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